In the small-scale production of beer and wine, there are wide ranges of process variables that can positively or negatively affect the outcome of the final product. Of these process variables, temperature is one of the most significant. While a particular batch of beer or wine may be of very high quality, without specific production controls, it may be difficult to consistently produce a high quality product. Fluctuations in fermentation temperature profiles, even while holding all other factors constant, can have a significant impact on the character and quality of the final product. Large seasonal differentials in ambient temperature can influence the fermentation process, and for some products, the daily fluctuation in ambient temperature can negatively impact the fermentation process.
In the production of beer, controlling temperature is critical during most phases of the process. From the production of the wort (a solution of fermentable and non-fermentable sugars) during the mash, though to the final fermentation of the beer, the temperature profile determines the character and quality of the final product. For example, during the mash, a brewer can extract different sugars from the malt and adjuncts based on the temperature and duration of the rests. If the brewer uses a lower temperature, the brewer can extract more fermentable sugars, increasing potential alcohol content and making a lighter style beverage. If the brewer uses a higher temperature, more non-fermentable sugars can be extracted, generating wort that is less fermentable, but with more of a characteristic referred to as “mouthfeel.” During the mash, temperature selection and control is critical for extracting the desired fermentable and non-fermentable profile needed produce the end product.
During the beer fermentation stage, the desired temperature can depend on multiple characteristics. Different yeast strains require different temperatures, and different temperatures with a given yeast strain can significantly affect the character, quality, and consistency of the final product. For beer, the fermentation process is responsible for approximately 50% to 70% of the flavor profile. Lager yeasts perform better between approximately 7.22° C. (45° F.) to 12.78° C. (55° F.), while ale yeasts prefer temperatures around 15.56° C. (60° F.) to 21.11° C. (70° F.). If the temperature is too low, the yeast may become dormant. If the temperature is too high, the yeast may produce undesirable byproducts such as some esters, fusel alcohols, and too much diacetyl (e.g., butane-2,3-dione).
As with beer, the type of wine yeast determines the appropriate fermentation temperatures. Wine yeast strains can perform well with temperature ranges from the low 50's to the high 80's. For wine, cooler fermentation temperatures tend to preserve the nature of the fruit (such as aroma and a clean, crisp sensation); whereas warmer fermentation temperatures tend to produce more “complexity” and “mouthfeel”, but the original nature of the fruit is diminished. If the fermentation temperature is too high, undesirable amounts of Hydrogen Sulfide (H2S) are produced. Accordingly, it is critical to control fermentation temperatures to ensure the final product matches the intensions of the brewer/winemaker.